In a work machine represented by a hydraulic excavator, an idle stop technology for automatically stopping an engine during non-work in order to reduce the fuel consumption, the amount of carbon oxide and noise is known.
In the idle stop technology, an invention is known in which, in order to avoid cumbersomeness in operation by an operator, a sensor is provided at means other than means for turning an engine key, for example, at an operation lever or in the proximity of the operation lever such that the engine is restarted from the idle stop state in response to a detection value of the sensor (for example, refer to Patent Document 1).